1. Field of the Invention
The present invention relates to a battery module in which cooling efficiency of unit rechargeable battery cells is improved.
2. Description of Related Art
A rechargeable battery may be formed with various shapes, such as a cylindrical shape and a prismatic shape. In order to drive a motor for the electric vehicle requiring high electrical power, a plurality of rechargeable battery cells are serially connected to each other to thereby form a high-capacity rechargeable battery module.
A rechargeable battery module is typically constructed by serially interconnecting a plurality of rechargeable battery cells (referred to simply as the “unit cells”).
The respective unit cells each include an electrode assembly with positive and negative electrode plates between which a separator is interposed. A case mounts the electrode assembly therein. A cap assembly is fitted to the case to seal it, and positive and negative electrode terminals are electrically connected to current collectors of the positive and the negative electrode plates of the electrode assembly.
With the usual prismatic batteries, the respective unit cells are arranged such that the positive and the negative electrode terminals thereof protrude from the top of the cap assembly and alternate with those of a neighboring unit cell. A conductor interconnects the screwed negative and positive electrode terminals via a nut, thereby constructing a battery module.
Since the battery module is typically constructed by interconnecting several to several tens of unit cells, the heat generated at the respective unit cells needs to be effectively dissipated such that the temperature difference between locations of the respective unit cells within the battery module is minimized to avoid deteriorating the battery capacity.
When heat dissipation is not done effectively, the temperature deviation between the respective unit cells deteriorates the battery charge/discharge efficiency. The internal temperature of the battery can be elevated as a result of the heat generated from the unit cells so that not only is the battery capacity deteriorated, but in a severe case, the battery can explode.
Further, when the battery module is used to drive a motor for an electronic washer, an electric scooter or a vehicle (an electric vehicle or a hybrid electric vehicle), it is charged and discharged by a high electric current so that the internal temperature may be elevated a considerable degree due to the heat generated by the internal reaction of the unit cells during usage. This can badly affect the battery characteristics, and deteriorates the inherent battery capacity. Accordingly, it becomes important for high capacity battery modules that their construction provides for appropriate heat dissipation.